Explanation
Port 53 is the standard port for DNS (Domain Name System) queries and responses. DNS is a service that translates domain names (such as www.example.com) into IP addresses (such as 192.0.2.1) and vice versa. DNS is essential for internet connectivity, as it allows users and applications to access websites and other online resources by using human-readable names instead ofnumerical addresses1.
The DNSSrv server is a DNS server that provides name resolution for the corporate network. If port 53 is blocked on this server, it will not be able to communicate with other DNS servers or clients, and the name resolution will fail. This will prevent users from accessing any websites or online services that rely on domain names, such as web browsers, email clients, or cloud applications. Therefore, port 53 must remain open on DNSSrv to allow DNS traffic to flow.

The tool that the administrator should use to check for unnecessary running services across 12 servers is a port scanner. A port scanner is a tool that scans a network device for open ports and identifies the services or applications that are running on those ports. A port scanner can help detect any unauthorized or unwanted services that may pose a security risk or consume network resources. A port scanner can also help troubleshoot network connectivity issues or verify firewall rules.